9328900990 Rev L BE1-951 General Information 1-1
SECTION 1 • GENERAL INFORMATION
DESCRIPTION
The BE1-951 Overcurrent Protection System is an economical, microprocessor based, multifunction
system that is available in a drawout, H1 (half-rack), S1, and S1 double-ended packages. BE1-951
features include:
• Directional Three-Phase Overcurrent Protection
• Directional Ground Overcurrent Protection
• Directional Negative-Sequence Overcurrent Protection
• Directional Power Protection
• Control Protection
• Breaker Failure Protection
• Automatic Reclosing
• Voltage Protection
• Frequency Protection
• Breaker Monitoring
• Metering Functions
• Communication
BE1-951 relays have four programmable contact sensing inputs, five programmable outputs, and one
alarm output. Outputs can be assigned to perform protection, control, or indicator operations through
logical programming. For example, protection functions could be programmed to cause a protective trip.
Control functions could be programmed to cause a manual trip, manual close, or automatic reclose.
Indicators could be configured to annunciate relay failure, a settings group change, and others.
Protection scheme designers may select from a number of pre-programmed logic schemes that perform
the most common protection and control requirements. Alternately, a custom scheme can be created
using BESTlogic.
A simplified Getting Started procedure for BE1-951 users is provided in Section 2, Quick Start.
FEATURES
The BE1-951 relay includes many features for the protection, monitoring, and control of power system
equipment. These features include protection and control functions, metering functions, and reporting and
alarm functions. A highly flexible programmable logic system called BESTlogic allows the user to apply
the available functions with complete flexibility and customize the system to meet the requirements of the
protected power system. Programmable I/O, extensive communication features, and an advanced HMI
(human-machine interface) provide easy access to the features provided.
The following information summarizes the capabilities of this multifunction device. Each feature, along
with how to set it up and how to use its outputs is described in complete detail in the later sections of this
manual.
Input and Output Functions
Input functions consist of Power System Measurement and Contact Sensing Inputs. Programmable
Contact Outputs make up the output functions. Input and Output functions are described in the following
paragraphs.
Power System Measurement Functions
Three-phase currents and voltages are digitally sampled and the fundamental is extracted using a
Discrete Fourier Transform (DFT) algorithm.
The voltage sensing circuits automatically configure themselves internally for single-phase, three wire or
four wire voltage transformer circuits. Voltage sensing circuitry provides voltage protection, frequency
protection, and watt/var metering. Neutral (residual) and negative voltage magnitudes are derived from
the three-phase voltages. Digital sampling of the measured frequency provides high accuracy at off-
nominal values.
An auxiliary voltage sensing input provides protection capabilities for over/undervoltage monitoring of the
first and third harmonic of the VT source connected to the Vx input. This capability is useful for ground
fault protection or sync-check functions.
Each current sensing circuit is low burden and isolated. Neutral (residual) and negative current
magnitudes are derived from the three-phase currents. An optional independent ground current input is
available for direct measurement of the current in a transformer neutral, tertiary winding, or flux balancing
current transformer.
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